Organic pigments

ABSTRACT

Disclosed are novel organic pigments adapted particularly for use as fillers for paper. The organic pigments are finely divided particles obtained by graft copolymerizing an ethylenically unsaturated monomer, such as styrene, onto a water-soluble cationic prepolymer in an aqueous solution and in the presence of a free-radical polymerization initiator.

This application is a division of application Ser. No. 159,744, filed 16June 1980, U.S. Pat. No. 4,349,641. Application Ser. No. 159,744 is adivision of application Ser. No. 909,606, filed 25 May 1978, now U.S.Pat. No. 4,235,982. Application Ser. No. 909,606 is acontinuation-in-part of application Ser. No. 803,330, filed 3 June 1977,now abandoned.

This invention relates to novel organic pigments adapted particularlyfor use as paper fillers.

Paper is often filled with mineral fillers such as clay, calciumcarbonate or titanium dioxide. The function of a mineral filler is toincrease the opacity of the paper and prevent "show-through"; lowopacity leads to page-to-page show-through in printed matter such asbooks, magazines and newspapers. While the mineral fillers perform thisfunction very well at relatively low cost, they also have disadvantages.First, they reduce paper strength substantially. This can cause problemsin later use, but more importantly, low sheet strength can make itnecessary to run the paper machine at slower speeds. The seconddisadvantage is that the mineral fillers have relatively high densities(sp. gr. 2.5-4.0) and thus increase the weight of filled paper. This isbecoming more of a problem as the rising cost of mailing printedmaterial, such as magazines, is increasing the demand for lightweightpaper. Thus, there is a need in the paper industry for a low densityopacifier for paper that will not adversely affect the strength of thepaper.

The use of latex particles as lightweight fillers for paper is known inthe art. Polystyrene latexes are commercially available for thisapplication. Like mineral fillers, these polystyrene latexes consist ofanionic particles that require cationic retention aids for goodretention on anionic pulp fibers. In addition, polystyrene latex fillersdecrease the strength of filled paper, although less than mineralfillers do.

Also, small particles of urea-formaldehyde resin have been used as paperfillers. It is reported that these particles are lightweight and, whenused as paper fillers, improve opacity, brightness, smoothness and bulkof the paper; however, they have an adverse effect on paper strength,altough this effect is reported to be less than that of the mineralfillers.

Disclosed in U.S. Pat. No. 3,824,114 are microcapsules having a solidpolymeric shell and a solid, non-tacky polymeric core which is graftedto the polymeric shell. The microcapsules may be coated onto cellulosicsubstrates or incorporated into such substrates and subsequently fusedto provide cellulosic substrates having a polymeric film bonded theretoand increased strength, respectively. This patent states at col. 3,lines 29-40 that the polymer containing microcapsules may be formedhaving an average particle diameter of between about 0.5 and about 1.0micron. It is stated also that the particles are capable of impartinghigh opacity to surface coatings of various substrates. It is alsostated that the microcapsules may be interspersed with cellulose fibersand formed into a web of such fibers and that the polymericmicrocapsules act as non-abrasive, opacifying agents and impart a highopacity to the cellulose substrate ultimately formed.

An object of this invention is to provide organic pigments that can beused as fillers for lightweight paper and that provide opacity,brightness and smoothness without adversely affecting paper strength. Afurther object of this invention is to provide organic pigments that areself-retaining during the paper making process; that is, the organicpigments are well retained on pulp fibers without the use ofconventional retention aids.

In accordance with this invention, there are provided graft copolymerparticles, suitable for use as organic pigments and particularly aspaper fillers, and consisting essentially of the free radical catalyzedgraft copolymerization product of (1) at least one ethylenicallyunsaturated monomer and (2) a water-soluble cationic prepolymer havingan RSV of about 0.1 to about 2.5 (1 M NaCl, 1%, 25° C.), the prepolymermoiety of the graft copolymer particles being present on the surface ofthe particles, said monomer (1) being selected from the group consistingof methyl alpha-chloroacrylate, ethyl alpha-chloroacrylate, methylmethacrylate, isopropyl methacrylate, phenyl methacrylate, vinylchloride, acrylonitrile, methacrylonitrile, and monomers having theformula ##STR1## wherein R is hydrogen or methyl, Y is methyl orchlorine, and n is 0, 1, 2, or 3, and said prepolymer (2) being theaddition polymerization product of

(i) about 5 mole percent to 100 mole percent of at least one cationicmonomer selected from the group consisting of ##STR2## wherein R₁ ishydrogen or methyl, R₂ is hydrogen or a C₁ -C₄ alkyl, R₃ is hydrogen, aC₁ -C₄ alkyl, ##STR3## where Y is hydroxyl or halogen, ##STR4## and--CH₂ CH₂ O)_(n) H where n is an integer 1 or more and X⁻ is an anion,##STR5## wherein R₁ is hydrogen or a C₁ -C₄ alkyl, R₂ is hydrogen, alkylor substituted alkyl, and R₃ and X⁻ are as defined in formula (I),##STR6## wherein R₁, R₂, R₃ and X⁻ are as defined in formula (I),##STR7## wherein R₁, R₃ and X⁻ are as defined in formula (I), ##STR8##wherein R₁, R₂, R₃ and X⁻ are as defined in formula (I), and n is aninteger 1, 2 or 3 and ##STR9## wherein R₁, R₂, R₃ and X⁻ are as definedin formula (I), and

(ii) from about 95 mole percent to 0 mole percent of at least oneethylenically unsaturated nonionic monomer selected from the groupconsisting of N-vinyl pyrrolidone, ethylenically unsaturated monomershaving amide functionality, and ethylenically unsaturated monomershaving hydroxyl functionality,

the amount of prepolymer (2) employed in preparing the graft copolymerparticles being from about 1 part to about 25 parts by weight for each100 parts by weight of monomer (1) employed. Substantially all thecationic prepolymer moiety of the graft copolymer particles is on thesurface of the resulting particles.

When the graft copolymer particles of this invention are suspended inwater in the presence of cellulosic pulp fibers, they are attracted tothe anionic sites on the surface of the fibers and adhere to the pulpfibers. During the paper making process, which comprises drainage ofwater from a slurry of pulp fibers, the cationic particles remain withthe pulp fibers and are thus well retained in the paper.

Graft copolymer particles prepared using water-soluble prepolymerscontaining an optimum level of cationic functionality are self-retainedduring the papermaking process; that is, when these particles areslurried with pulp fibers prior to sheet formation, the particles adherestrongly to the anionic pulp fibers and very little, if any, are lostwhen the water is filtered off during the paper making process. Thus, noretention aid is required to keep the particles with the pulp fibers.However, known retention aids can be used in the paper making process,if desired. In addition, paper filled with graft copolymer particlesprepared according to this invention has strength properties usuallyequivalent to and sometimes better than unfilled paper of the sameweight. Papers filled with mineral pigments, such as clay or titaniumdioxide, have substantially lower strength properties than thecorresponding unfilled paper.

The monomers used to prepare these particles are such that they willgraft polymerize onto the cationic water-soluble prepolymer to form awater-insoluble graft copolymer. It is the insolubility of the graftcopolymer that leads to the formation of discrete, essentially sphericalparticles suspended in water. The initial function of the water-solublecationic prepolymer is to stabilize the suspension and preventcoagulation of the individual particles. After initial graftcopolymerization is effected some homopolymerization of the monomer mayoccur inside the particles. Essentially stable latexes of the graftcopolymer particles are prepared in accordance with this inventionwithout requiring the presence of an additional stabilizer. There aretwo main requirements for the graft copolymer particles prepared inaccordance with this invention. They must (1) be water-insoluble and (2)have a high enough melting or softening point that they will not bedeformed to any substantial degree under the conditions of heat orpressure or both to which they will be subjected in use. Use as fillersfor paper requires that the particles remain discrete and essentiallyspherical during web formation, drying and calendering. Preferably, thegraft copolymer will have a second order transition temperature (glasstransition temperature, Tg) of about 75° C. or greater. All the graftcopolymers prepared by the working examples that follow have a Tggreater than 75° C.

Any monomer that will graft copolymerize with the water-soluble cationicprepolymers, hereinafter described, to provide graft copolymer particlesmeeting the above requirements can be employed in this invention.Suitable monomers are monoethylenically unsaturated monomers such, forexample, as acrylic esters such as methyl α-chloroacrylate and ethylα-chloroacrylate; methacrylic esters such as methyl methacrylate,isopropyl methacrylate and phenyl methacrylate; monomers having theformula ##STR10## where R is hydrogen or methyl, Y is methyl or chlorineand n is 0, 1, 2 or 3. Examples of such monomers are styrene, α-methylstyrene, monochlorostyrene, dichlorostyrene, trichlorostyrene,monomethylstyrene, dimethylstyrene and trimethylstyrene. Other suitablemonomers are vinyl chloride, acrylonitrile and methacrylonitrile.

Mixtures of two or more monoethylenically unsaturated monomers can beused in carrying out this invention provided the resulting graftcopolymer particles are water-insoluble and have a T_(g) of about 75° C.or greater. Also polyethylenically unsaturated monomers, such asdivinylbenzene, can be used in admixture with monoethylenicallyunsaturated monomers to provide crosslinked graft copolymer particles.Of the above listed monoethylenically unsaturated monomers, styrene,vinyl chloride, acrylonitrile and methyl methacrylate are preferred.

The water-soluble cationic prepolymer can be any of a variety ofpolymers. The main criterion is that it provide the optimum cationiccharge for good retention of the resulting graft copolymer particles inpaper. For example, in a latex prepared using about 10% prepolymer basedon the weight of the monomer used, opacity is highest when the molepercent of the cationic monomer moiety of the water-soluble prepolymeris in the range of about 5 to 50, with the optimum range being fromabout 10 to about 30 mole percent. These ranges are, of course,dependent on the level of water-soluble cationic prepolymer used toprepare the latex. Thus when about 5% water-soluble prepolymer based onmonomer is used, the range would be about 10 to about 100 mole percentcationic monomer moiety with the optimum range being from about 20 toabout 60 mole percent. Similar corrections can be made when other levelsof water-soluble polymer are used and are within the skill of the art.

The cationic water-soluble prepolymers that are particularly suitablefor use in this invention are addition-type polymers prepared fromethylenically unsaturated cationic monomers having the formulas (I),(II), (III), (IV), (V) and (VI) below. ##STR11## In formula (I), R₁ ishydrogen or methyl; R₂ is hydrogen or a C₁ -C₄ alkyl such as methyl,ethyl, propyl, or butyl; R₃ is hydrogen, a C₁ -C₄ alkyl, ##STR12## whereY is hydroxyl or halogen such as chlorine and bromine, ##STR13## and(CH₂ CH₂ O)_(n) H where n is an integer 1 or more, preferably 1 through20; and X⁻ is an anion such as Cl⁻, Br⁻, CH₃ OSO₃ ⁻ and CH₃ COO⁻.Monomers of formula (I) are quaternary ammonium salts and acid salts ofamino acrylates such as dimethylaminoethylacrylate,diethylaminoethylacrylate, dimethylaminoethylmethacrylate, anddiethylaminoethylmethacrylate. Specific quaternary salt monomers havingthe formula (I) are methacryloyloxyethyltrimethylammonium methyl sulfateand methacryloyloxyethyltrimethylammonium chloride. Specific acid saltmonomers having the formula (I) are methacryloyloxyethyldimethylammoniumchloride and methacryloyloxyethyldimethylammonium acetate. ##STR14## Informula (II), R₁ is hydrogen or a C₁ -C₄ alkyl. R₂ is hydrogen, alkyl orsubstituted alkyl, Typical alkyl groups, which R₂ can be, contain from 1through 18 carbon atoms, preferably from 1 through 6, and includemethyl, ethyl, propyl, isopropyl, t-butyl, hexyl, octyl, decyl, dodecyl,tetradecyl, and octadecyl. R₂ can also be a substituted alkyl, suitablesubstituents being any substituent that will not interfere withpolymerization through a vinyl double bond. Typically the substituentscan be carboxylate, cyano, ether, amino (primary, secondary ortertiary), amide, hydrazide and hydroxyl, R₃ and X⁻ are as defined informula (I). The formula (II) monomers are quaternary ammonium salts andacid salts of a diallylamine having the formula ##STR15## where R₁ andR₂ are as above defined. Specific examples of quaternary ammonium saltmonomers having formula (II) are dimethyldiallylammonium chloride anddimethyldiallylammonium bromide. Specific examples of acid salt monomershaving formula (II) are methyldiallylammonium acetate, diallylammoniumchloride, N-methyldiallylammonium bromide,2,2'-dimethyl-N-methyldiallylammonium chloride, N-ethyldiallylammoniumbromide, N-isopropyldiallylammonium chloride, N-n-butyldiallylammoniumbromide, N-tert-butyldiallylammonium chloride, N-n-hexyldiallylammoniumchloride, N-octadecyldiallylammonium chloride,N-acetamidodiallylammonium chloride, N-cyanomethyldiallylammoniumchloride, N-propionamidodiallylammonium bromide, N-acetic ethyl estersubstituted diallylammonium chloride, N-ethylmethylether substituteddiallylammonium bromide, N-ethylaminediallylammonium chloride,N-hydroxyethyldiallylammonium bromide and N-aceto-hydrazide substituteddiallylammonium chloride. ##STR16## In formula (III), R₁, R₂, R₃ and X⁻are as defined in formula (I). Specific examples of monomers of formula(III) are vinylbenzyltrimethylammonium chloride andvinylbenzyltrimethylammonium bromide. ##STR17## In formula (IV), R₁, R₃and X⁻ are as defined in formula (I). Specific examples of monomers offormula (IV) are 2-vinylpyridinium chloride and 2-vinylpyridiniumbromide. ##STR18## In formula (V), R₁, R₂, R₃ and X⁻ are as defined informula (I), and n is an integer 1, 2 or 3. A specific example of amonomer of formula (V) is methacrylamidopropyldimethylammonium chloride.##STR19## In formula (VI), R₁, R₂, R₃ and X⁻ are as defined in fornula(I). A specific example of a monomer of formula (VI) is3-methacryloyloxy-2-hydroxypropyldimethylammonium chloride.

The water-soluble cationic prepolymer used in this invention can also bea naturally occurring polymer such as casein or a derivative of anaturally occurring polymer such as chitosan.

As set forth above, there is an optimum level of cationic charge on thepolymer particle required for good retention in paper. The optimumcharge can be achieved with a cationic homopolymer by varying the amountof homopolymer used to prepare the graft copolymer latex. It ispreferred however to adjust the cationic charge by using a copolymer ofat least one cationic monomer and at least one nonionic unsaturatedmonomer capable of addition-type polymerization. Examples of nonionicmonomers are monoethylenically unsaturated amide monomers such asacrylamide; methacrylamide; N-acetamidoacrylamide;N-acetamidomethacrylamide; N-methylolacrylamide; diacetoneacrylamide;diacetonemethacrylamide; N,N-dimethylacrylamide; and N-methylacrylamide.Other suitable nonionic monomers are vinyl acetate;2-hydroxyethylacrylate; 2-hydroxyethylmethacrylate; andN-vinylpyrrolidone. Copolymers of vinyl acetate are subsequentlyhydrolyzed to replace essentially all the acetate groups with hydroxylgroups.

The water-soluble cationic prepolymers used in this invention can be (A)homopolymers of the cationic monomers shown in formulas (I) through(VI): (B) copolymers of any two or more of the monomers shown informulas (I) through (VI); and (C) copolymers of at least one of themonomers shown in formulas (I) through (VI) and at least one otherethylenically unsaturated monomer, preferably a nonionic monomer. Thus,the preferred water-soluble cationic prepolymers will consistessentially of from about 5 mole percent to 100 mole percent of at leastone monomer shown in formulas (I) through (VI) and from about 95 molepercent to 0 mole percent of at least one other ethylenicallyunsaturated nonionic monomer.

Highly satisfactory water-soluble cationic prepolymers for use inpreparing the graft copolymer particles of this invention are (1) theprepolymers prepared from about 70 mole % to about 98 mole %, preferablyfrom about 82 mole % to about 90 mole %, acrylamide and from about 30mole % to about 2 mole %, preferably from about 18 mole % to about 10mole % dimethyldiallylammonium chloride; (2) the prepolymers preparedfrom about 67 mole % to about 98 mole %, preferably from about 67 mole %to about 89 mole %, acrylamide and from about 33 mole % to about 2 mole%, preferably from about 33 mole % to about 11 mole %,methyldiallylammonium chloride; (3) the prepolymers prepared from about70 mole % to about 98 mole %, preferably from about 82 mole % to about91 mole %, acrylamide and from about 30 mole % to about 2 mole %,preferably from about 18 mole % to about 9 mole %, methyldiallylammoniumacetate; and (4) the prepolymers prepared from about 70 mole % to about95 mole %, preferably from about 70 mole % to about 88 mole % acrylamideand from about 30 mole % to about 5 mole %, preferably from about 30mole % to about 12 mole %, methacryloyloxyethyltrimethylammonium methylsulfate.

The water-soluble cationic prepolymers are easily and readily preparedby adding, simultaneously, the desired monomers, in the desired amounts,and a water-soluble free-radical polymerization initiator, each inaqueous solution, to a reaction vessel containing water maintained at atemperature of about 80° C. to about 90° C. Suitable free-radicalpolymerization initiators are those employed in preparing the graftcopolymer particles of this invention and which are set forth hereafter.The amount of initiator employed will be that amount sufficient toprovide water-soluble cationic prepolymers having an RSV of from about0.1 to about 2.5, preferably from about 0.1 to about 1.0, measured as a1% solution in 1 M NaCl at 25° C.

In some cases, it is desirable to have reactive functionality, that is,reactive groups on the surface of the graft copolymer particles. Thereactive groups generally increase the bonding properties of the graftcopolymer particles. Preferred reactive groups are those that react withcellulose.

Reactive groups can be introduced into the cationic monomer prior topreparation of the prepolymer, or they can be introduced into theprepolymer after preparation thereof, or they can be introduced into thegraft copolymer particles after their preparation.

Cellulose reactive groups can be introduced by reacting anepihalohydrin, such as epichlorohydrin, with polymers containingsecondary amine functionality, or tertiary amine functionality, or both.Reactive groups provided by epihalohydrin can be an epoxide, thehalohydrin form of the epoxide, or an azetedinium group.

Reactive groups can be introduced by means of an aldehyde such asformaldehyde, glyoxal and glutaraldehyde with polymers containing amidefunctionality, such as those prepolymers prepared by copolymerizing acationic monomer and acrylamide or those polymers containing secondaryamine functionality such as in prepolymers prepared from diallylaminesalts. Using dialdehydes, such as glyoxal, the reactive group will be analdehyde. Using formaldehyde, the reactive group will be the N-methylolgroup.

The amount of functionalizing agent employed to provide reactive groupson the graft copolymer particles of this invention will be about 0.25mole to about 3 moles, preferably about 1 mole to about 2 moles, foreach mole of amide or amine functionality.

Reaction will be carried out at a temperature of from about 20° C. toabout 60° C. at a pH of about 8 to 10 except when formaldehyde is usedas the functionalizing agent, reaction is carried out at a pH of fromabout 2 to 3.

The reactive groups can improve paper strength by providing a means forthe graft copolymer particles to react with cellulose fibers.Conventional fillers generally decrease paper strength by interferingwith bonding between cellulose fibers. By use of graft copolymerparticles having cellulose reactive groups, it is possible to obtainhigher paper strength through bonding between fibers through thereactive functional groups on the particles.

The amount of prepolymer used in preparing the graft copolymers of thisinvention can vary from about 1 part to about 25 parts by weight foreach 100 parts by weight of monomer employed. The preferred range isfrom about 2 to about 10 parts of prepolymer for each 100 parts ofmonomer.

Graft copolymerization is carried out by adding monomer to an aqueoussolution of water-soluble cationic prepolymer in the presence of afree-radical polymerization initiator. The water-soluble prepolymer canall be present in the reaction vessel at the beginning of the run, orall or part of it can be added simultaneously with the monomer. Theinitiator is usually added continuously along with the monomer. Thetotal reaction time can vary from about one hour to about 24 hours withthe preferred time being about 2 to 6 hours. Latexes prepared inaccordance with this invention will have a solids content of from about15% to about 60%. Preferably the amount of water employed in preparingthe latexes will be such as to provide latexes having a solids contentof from about 25% to about 55%. In some instances, it is possible to drythe latex to a fine powder. In these cases, the powder can beredispersed in water and then added to the pulp slurry prior toformation of the paper. Drying the latex to a fine powder is not usuallypossible when the graft copolymer particles have reactive functionality.

The final product is a stable suspension of essentially spherical graftcopolymer particles in water. In accordance with this invention graftcopolymer particles can be prepared that will have a particle size inthe range of about 0.1 micron to about 2 microns.

A wide variety of chemical polymerization initiators can be used toprepare the latexes of this invention, with peroxy compounds beingparticularly useful. Preferably the initiator will be water soluble.

Suitable water-soluble initiators include those activated by heat, suchas sodium persulfate and ammonium persulfate. Polymerizations carriedout with these initiators are generally run at temperatures of 70°-95°C. Other water-soluble initiators that are suitable include theso-called redox initiator systems such as ammonium persulfatesodiumbisulfite-ferrous ion and t-butyl hydroperoxide-sodium formaldehydesulfoxylate. Redox initiators are activated at relatively lowtemperatures, and polymerizations employing these systems can be carriedout at temperatures from about 20° C. to 80° C. The amount of initiatoremployed is within the skill of the art. Usually about 0.1 part to about5 parts by weight of initiator will be employed for each 100 parts byweight of monomer used.

The following examples illustrate the invention.

EXAMPLE 1

A water-jacketed resin kettle equipped with a thermometer, a stirrer, acondenser and three addition funnels was charged with 87.0 g. ofdistilled water. The funnels were charged with: (1) 71.25 g. acrylamide(1.0 mole) in 166.0 g. distilled water, (2) 3.75 g.dimethyldiallylammonium chloride (DMDAAC, 0.023 mole) in 8.75 g.distilled water, and (3) 1.88 g. ammonium persulfate (0.008 mole) in35.6 g. distilled water. The kettle contents were heated to 85°-89° C.,and the contents of the three funnels were added, dropwise, over aperiod of three hours. After heating for an additional fifteen minutes,the solution was cooled to room temperature (about 23° C.). The productsolution contained 21.9% solids and had an RSV, reduced specificviscosity, of 0.32 (1% solution in 1 M NaCl at 25° C.).

A water-jacketed resin kettle fitted with a thermometer, a stirrer, acondenser and three addition funnels was charged with 493.0 g. ofdistilled water and 54.4 g. of a 10% solids solution of the abovecopolymer (5.44 g. dry copolymer). The funnels were charged with: (1)164.0 g. of a 10% total solids solution of the above copolymer (16.4 g.dry copolymer), (2) 218.0 g. styrene and (3) 6.0 g. ammonium persulfatein 24.2 g. distilled water. The kettle contents were stirred and heatedto 88° C. The contents of the three funnels were added over a period ofthree hours as the kettle temperature was maintained at 88°-93° C. Afterheating for an additional fifteen minutes, the product was cooled toroom temperature. The product was a white latex containing 25.2% solids.Approximately half of the latex was dialyzed using a 48 angstromsregenerated cellulose membrane to remove unreacted water-solubleprepolymer.

A 240.0 g. sample of the dialyzed latex (50.0 g. dry polymer, 0.056 moleacrylamide) was placed in a reaction kettle, and the pH was adjustedfrom 4.2 to 9.1 with 0.9 ml. of 1 M sodium hydroxide solution. Glyoxal(16.2 g. of a 40% aqueous solution 0.112 mole) was added, and the pH wasadjusted from 6.2 to 9.0 with 0.8 ml. of 1 M sodium hydroxide solution.Water (56 ml.) was added to reduce the reaction solids. The mixture washeated for four hours at 50° C. and the pH was then lowered to 2.0 with0.5 ml. of concentrated hydrochloric acid. The final product contained18.2% solids.

EXAMPLES 2-5

Four additional latexes were prepared by the method described in Example1, except the ratio of acrylamide to DMDAAC was varied as shown in Table1 below.

                  TABLE 1                                                         ______________________________________                                        Prepolymer                                                                         Acryl-            (NH.sub.4).sub.2 --                                                                  Mole Ratio                                           amide   DMDAAC    S.sub.2 O.sub.8                                                                      Acrylamide:                                                                            %                                      Ex.  (g)     (g)       (g)    DMDAAC   T.S. RSV                               ______________________________________                                        1    71.25   3.75      1.88   97.75:2.25                                                                             21.9 0.32                              2    67.5    7.5       1.88   95:5     21.7 0.37                              3    60.0    15.0      1.88   90:10    21.6 0.28                              4    56.3    18.7      1.88   87:13    21.4 0.24                              5    37.5    37.5      1.88   70:30    21.3 0.18                              ______________________________________                                        Initial Latex                                                                 10% Pre-                             Particle                                 polymer    Sty-   (NH.sub.4).sub.2 --                                                                     % Solids Size -                                        Solution  rene   S.sub.2 O.sub.8                                                                       Pro- Dia-  micron                               Ex.  (g)       (g)    (g)     duct lyzed (1)                                  ______________________________________                                        1    218.4     218    6.0     25.2 20.8  0.4-0.6                              2    218.4     218    6.0     25.9 21.3  0.4-0.6                              3    218.4     218    6.0     26.1 19.7  0.4-1.0                              4    218.4     218    6.0     26.0 18.3  0.5-0.8                              5    218.4     218    6.0     25.2 17.6   0.8-1.26                            ______________________________________                                               Modified Latex                                                                  Dia-    40%                                                                   lyzed   Gly-             Product                                              Latex   oxal       Water % Total                                     Ex.      (g)     (g)        (g)   Solids                                      ______________________________________                                        1        240.0   16.2       56.0  18.2                                        2        234.0   13.9       60.0  18.2                                        3        250.0   12.2       39.0  18.3                                        4        218.0   9.2        14.0  18.3                                        5        226.6   5.8        2.0   17.9                                        ______________________________________                                         (g) = grams                                                                   (1) Particle size was measured by Transmission Electron Microscopy            T.S. = Total Solids                                                           RSV (reduced specific viscosity) measured as a 1% solution in 1M NaCl at      25° C.                                                            

EXAMPLE 6

The compositions of Examples 1-5 were evaluated as fillers for paper.Handsheets were prepared on a Noble & Wood handsheet apparatus. The pulpconsisted of a 50:50 blend of bleached hardwood:bleached softwood pulpsbeaten to a Canadian Standard Freeness of 300 cc. The paper was made ata pH of 4.5 (sulfuric acid, no alum). The latexes were evaluated ataddition levels of 4% and 8% (dry basis). The controls were unfilledpaper and paper filled with 10% and 20% kaolin clay. The clay wasretained through the use of 1% alum and 0.05% of a high molecular weightcationic polyacrylamide retention aid. The results of testing of thepaper are summarized in Table 2 below.

                                      TABLE 2                                     __________________________________________________________________________                             Basis        Dry                                                              Weight       Tensile                                                                            Mullen                                                      (lb./3000    Strength                                                                           Burst                              Filler (%)                                                                             Retention Aid   sq. ft.)                                                                           Opacity.sup.(1) (%)                                                                   (lb./in.)                                                                          (psi)                              __________________________________________________________________________    None     --              39.4 73.6    18.6 32.4                               Kaolin Clay (10)                                                                       Alum (1%) plus  41.9 80.3    15.0 25.7                               Kaolin Clay (20)                                                                       Cationic Polyacrylamide (.05%)                                                                44.6 84.5    13.5 22.4                               Example 1 (4)                                                                          --              39.6 74.3    19.6 36.3                               Example 1 (8)                                                                          --              40.5 75.1    19.8 34.3                               Example 2 (4)                                                                          --              40.0 78.0    19.9 37.3                               Example 2 (8)                                                                          --              40.7 82.7    20.2 38.1                               Example 3 (4)                                                                          --              40.1 80.0    20.4 37.3                               Example 3 (8)                                                                          --              41.4 85.1    19.8 34.5                               Example 4 (4)                                                                          --              40.2 81.5    19.2 34.3                               Example 4 (8)                                                                          --              41.6 86.3    19.0 33.9                               Example 5 (4)                                                                          --              40.2 79.3    19.7 34.3                               Example 5 (8)            41.1 83.8    18.4 33.9                               __________________________________________________________________________     .sup.(1) Opacity measured in accordance with Tappi Standard T425 (Hunter      Opacity Meter)                                                           

EXAMPLE 7-10

Four latexes were prepared by the method described in Example 1 using10% of various acrylamide-DMDAAC copolymers. The latexes were notreacted with glyoxal. The conditions for the latex syntheses areoutlined in Table 3.

EXAMPLE 11

The graft copolymers of Examples 7-10 were evaluated as fillers forpaper by the method described in Example 6. Test results are summarizedin Table 4.

EXAMPLES 12-16

Several latexes were prepared by the method described in Example 1 withthe exception that the water-soluble prepolymers used to prepare thegraft copolymers were copolymers of acrylamide andmethacryloyloxyethyltrimethylammonium methyl sulfate (MTMMS). Thereaction conditions are summarized in Table 5. The latexes were notreacted with glyoxal.

EXAMPLE 17

The graft copolymer particles of Examples 12-16 were evaluated asfillers for paper by the method described in Example 6. A commercialpolystyrene latex was used as an additional control in this experiment.The particles in the polystyrene latex bore negative charges and as aresult a retention aid was used as shown.

EXAMPLE 18

Clay and a commercial polystyrene latex were evaluated as fillers forpaper by the method described in Example 6. The two fillers wereevaluated both with and without a cationic polyacrylamide retention aid.Test results are summarized in Table 7.

                                      TABLE 3                                     __________________________________________________________________________    Water-Soluble Prepolymer          Latex                                                                         10%                                            Acryl-           Mole Ratio    Copolymer                                                                            Sty-           Particle                 amide                                                                             DMDAAC                                                                              (NH.sub.4).sub.2 S.sub.2 O.sub.8                                                     Acrylamide:                                                                          %      Solution                                                                             rene                                                                             (NH.sub.4).sub.2 S.sub.2                                                      O.sub.8 %   Size                  Ex.                                                                              (g.)                                                                              (g.)  (g.)   DMDAAC T.S.                                                                              RSV                                                                              (g.)   (g.)                                                                             (g.)    Solids                                                                            (μ)                __________________________________________________________________________    7  60.0                                                                              15.0  1.88   90:10  21.6                                                                              0.28                                                                             218.4  218                                                                              6.0     26.1                                                                              0.4-1.0.sup.(1)       8  56.3                                                                              18.7  1.88   87:13  21.4                                                                              0.24                                                                             218.4  218                                                                              6.0     26.0                                                                              0.5-1.0.sup.(1)       9  46.9                                                                              28.1  1.88   79:21  21.3                                                                              0.24                                                                             218.4  218                                                                              6.0     25.7                                                                               ˜0.5.sup.(2                                                            )                     10 37.5                                                                              37.5  1.88   70:30  21.3                                                                              0.18                                                                             218.4  218                                                                              6.0     26.2                                                                               0.8-1.26.sup.(1)     __________________________________________________________________________     .sup.(1) Particle size was measured by Transmission Electron Microscopy       .sup.(2) Particle size estimated by Light Microscopy                          (g.) = grams                                                                  T.S. = total solids                                                           RSV (reduced specific viscosity) measured as a 1% solution in 1M NaCl at      25° C.                                                            

                                      TABLE 4                                     __________________________________________________________________________                                           Dry Tensile                                                                          Mullen                                                     Basis Weight                                                                         Opacity.sup.(1)                                                                    Strength                                                                             Burst                           Filler (%)                                                                             Retention Aid     (lb/3000 ft..sup.2)                                                                  %    (lb./in.)                                                                            (psi)                           __________________________________________________________________________    None          --           40.7   75.2 16.3   31.4                            Kaolin Clay (10)                                                                         Alum (1%) plus  42.7   79.1 14.7   26.4                            Kaolin Clay (20)                                                                         Cationic Polyacrylamide (0.05%)                                                               44.3   81.0 15.3   25.0                            Example 7 (4)                                                                               --           41.7   80.2 16.9   30.1                            Example 7 (8)                                                                               --           42.9   84.5 15.7   28.1                            Example 8 (4)                                                                               --           41.6   81.7 15.7   30.0                            Example 8 (8)                                                                               --           42.8   86.0 15.2   26.6                            Example 9 (4)                                                                               --           41.8   81.6 15.3   28.8                            Example 9 (8)                                                                               --           42.9   86.3 14.1   25.9                            Example 10 (4)                                                                              --           41.2   79.3 15.5   28.0                            Example 10 (8)                                                                              --           41.9   82.9 15.1   27.9                            __________________________________________________________________________     .sup.(1) Opacity measured in accordance with Tappi Standard T425 (Hunter      Opacity Meter)                                                           

                                      TABLE 5                                     __________________________________________________________________________                                     Latex                                        Water-Soluble Prepolymer        10%                                              Acryl-          Mole Ratio   Copolymer                                                                           Sty-          Average.sup.1                amide                                                                             MTMMS                                                                              (NH.sub.4).sub.2 S.sub.2 O.sub.8                                                     Acrylamide:                                                                          %     Solution                                                                            rene                                                                             (NH.sub.4).sub.2 S.sub.2                                                             %.sub.8                                                                           Particle                  Ex.                                                                              (g.)                                                                              (g.) (g.)   MTMMS  T.S.                                                                             RSV                                                                              (g.)  (g.)                                                                             (g.)   Solids                                                                            Size                      __________________________________________________________________________                                                        (μ)                    12 120.0                                                                             180.0                                                                              22.5   70:30  21.6                                                                             0.16                                                                             2402  2398                                                                             66.0   26.0                                                                              0.8                       13 150.0                                                                             150.0                                                                              22.5   78:22  21.6                                                                             0.154                                                                            2402  2398                                                                             66.0   25.6                                                                              0.8                       14 201.0                                                                             99.0 22.5   88:12  21.8                                                                             0.187                                                                            2402  2398                                                                             66.0   25.6                                                                              0.7                       15 225.2                                                                             74.8 22.5   91:9   21.7                                                                             0.143                                                                            2402  2398                                                                             66.0   25.6                                                                              0.8                       16 255.0                                                                             45.0 22.5   95:5   21.7                                                                             0.168                                                                            2402  2398                                                                             66.0   24.7                                                                              0.8                       __________________________________________________________________________     g. = grams                                                                    .sup.1 Particle size was estimated from turbidity reading according to th     method of A. B. Lombel (Official Digest, 200, February, 1969).                T.S. = total solids                                                           RSV (reduced specific viscosity) measured as a 1% solution in 1M NaCl at      25° C.                                                            

                                      TABLE 6                                     __________________________________________________________________________                                             Dry Tensile                                                                          Mullen                                                    Basis Weight                                                                          Opacity.sup.(1)                                                                    Strength                                                                             Burst                         Filler (%)                                                                              Retention Aid     (lb./3000 sq. ft.)                                                                    %    (lb./in.)                                                                            (psi)                         __________________________________________________________________________    None        --              39.9    79.6 18.2   30.5                          Kaolin Clay                                                                          (10) Alum (1%) plus  44.5    86.0 13.9   21.5                                 (20) Cationic Polyacrylamide                                                                       48.9    89.4 11.6   16.5                                      (0.05%)                                                           Example 12                                                                           (4)  --              40.6    85.0 17.5   29.1                                 (8)  --              42.1    89.4 14.8   24.4                          Example 13                                                                           (4)  --              40.7    85.1 17.9   30.4                                 (8)  --              41.4    89.1 16.0   33.0                          Example 14                                                                           (4)  --              40.8    83.9 17.2   29.5                                 (8)  --              41.4    88.0 15.4   26.6                          Example 15                                                                           (4)  --              39.6    81.0 18.4   31.1                                 (8)  --              40.6    83.9 18.3   31.9                          Example 16                                                                           (4)  --              39.6    78.3 17.3   32.6                                 (8)  --              39.5    78.5 17.9   30.8                          Commercial  Alum (1%) plus  40.9    86.5 15.5   24.0                          Polystyrene                                                                          (4)                                                                           (8)  Cationic Polyacrylamide (0.05%)                                                               43.0    90.6 14.1   19.9                          __________________________________________________________________________      .sup.(1) Opacity measured in accordance with Tappi Standard T425 (Diano      Opacimeter)                                                              

                  TABLE 7                                                         ______________________________________                                                            Basis                                                                         Weight        Dry                                                             (lb./   Opa-  Tensile                                                                              Mullen                                        Retention  3000    city.sup.(1)                                                                        Strength                                                                             Burst                                Filler (%)                                                                             Aids       sq. ft.)                                                                              (%)   (lb./in.)                                                                            (psi)                                ______________________________________                                        Kaolin   Alum (1%)  40.3    75.9  16.2   28.9                                 Clay (10)                                                                     Kaolin   Alum (1%)  42.8    80.4  16.2   26.7                                 Clay (10)                                                                              plus                                                                          Cationic                                                                      Polyacryl-                                                                    amide (.05%)                                                         Commercial                                                                             Alum (1%)  39.8    76.3  18.9   30.6                                 Polystyrene                                                                   (4)                                                                           Commercial                                                                             Alum (1%)  40.8    80.5  18.3   29.4                                 Polystyrene                                                                            plus                                                                 (4)      Cationic                                                                      Polyacryl-                                                                    amide (.05%)                                                         ______________________________________                                         .sup.(1) Opacity measured in accordance with Tappi Standard T425 (Hunter      Opacity Meter)                                                           

EXAMPLE 19

Dimethylaminoethylmethacrylate (157 g.) was added dropwise to 98 g. of37% hydrochloric acid. Cooling was necessary to maintain the temperaturebelow 30° C. Water (381 cc.) and isopropanol (12.2 cc.) were addedgiving a 30% solution. This solution was heated to 50° C. and spargedwith nitrogen for 30 minutes followed by heating to 75° C. and adding3.6 cc of 0.1 M FeSO₄ 7H₂ O followed by 10.9 cc. of t-butylhydroperoxide(90%). When the catalyst addition was completed the solution was stirredfor 30 minutes and cooled to room temperature. The viscous solution wasdiluted to 15.85% solids. RSV=0.53 (1 M NaCl, 1%, 25° C.).

A water-jacketed two liter resin kettle equipped with a thermometer,stirrer, condenser, and three addition funnels was charged with 269 cc.of distilled water. The funnels were charged with: (1) 183 g. of a 12.3%aqueous solution of the poly(methacryloyloxyethyldimethylammoniumchloride), prepared as above, (2) 225 g. styrene and (3) 6 g. ammoniumpersulfate in 25 cc. of distilled water. The contents of the kettle werestirred and heated to 88° C. under nitrogen. The contents of the funnelswere added, dropwise, over a period of two hours as the kettletemperature was maintained at 88°-95.5° C. After heating for anadditional fifteen minutes, the product was cooled to room temperature.The final product was free of styrene and had a total solids of 36.4%.

EXAMPLE 20

Poly(methacryloyloxyethyldimethylammonium chloride) was prepared as inExample 19 except the solution was diluted to 30% solids instead of15.85%. 161.5 g. of this 30% solution was placed into a reaction vesselwith 359 g. distilled water. The pH of the solution was adjusted from1.9 to 1.0 with 3.6 cc. of concentrated HCl. Epichlorohydrin (34.7 g.)was added to the reaction vessel giving 15% reaction solids. Thismixture was stirred for 6.5 hours after which time the pH rose to 7.6.The pH was then adjusted to 0.5 with 13.7 cc. of concentrated HCl. Totalsolids=12.3%.

A water-jacketed two liter resin kettle equipped with a thermometer,stirrer, condenser, and three addition funnels was charged with 269 cc.of distilled water. The funnels were charged with (1) 183 g. of a 12.3%aqueous solution of the water-soluble epichlorohydrin modifiedprepolymer prepared as above, (2) 225 g. styrene and (3) 6 g. ammoniumpersulfate in 25 cc. of distilled water. The contents of the kettle werestirred and heated to 89° C. under nitrogen. The contents of the funnelswere added, dropwise, over a period of two hours as the kettletemperature was maintained at 89°-97° C. After heating for an additionalfifteen minutes, the product was cooled to room temperature. The finalproduct was free of styrene and had a total solids of 36.8%.

EXAMPLE 21

A reaction kettle was charged with 4130 g. of distilled water and 145.5g. of a 51.95% aqueous solution of poly(methyldiallylammonium chloride).The contents of the kettle were heated to 87° C. under nitrogen. 228 g.poly(methyldiallylammonium chloride) in 1597 g. of distilled water, 3040g. styrene, and 83.7 g. ammonium persulfate in 338 g. of distilled waterwere added simultaneously, dropwise, over a period of two hours. Thetemperature was maintained at 87°-100° C. The contents of the kettlewere stirred for an additional 15 minutes, cooled to room temperatureand filtered through a 100-mesh screen. The resulting latex had a totalsolids of 37.2% and the particle size was 0.5 micron as measured by theLoebel Method (see Table 5) 806.5 g. of the above latex (300 g. solids)was placed into a reaction flask and the pH adjusted from 1.6 to 1.1with 8.8 cc. of concentrated hydrochloric acid. Epichlorohydrin (34.2g.) was added followed by stirring at room temperature. As the reactionprogressed the pH rose to 7.3 at which time the pH was adjusted to 1.55with concentrated hydrochloric acid. The resulting latex had a solidscontent of 37%.

EXAMPLE 22

A reaction vessel was charged with 200 g. of distilled water, 0.24 g.acetic acid, 3.64 g. sodium acetate and 1 g. isopropanol. This washeated to 60° C. under nitrogen and held for 15 minutes.Methylolacrylamide (40 g. in 160 g. distilled water),methyldiallylammonium chloride (13.3 g. in 53.1 g. distilled water) andammonium persulfate (0.8 g. in 20 g. distilled water) were addedsimultaneously, dropwise, over a period of about 1.8 hours, followed bystirring for one hour. The viscous copolymer solution was cooled to roomtemperature and the pH adjusted from 5.0 to 7.2 with 1.4 cc. of 5 MNaOH. Total solids of the reaction mass was 12.8%. The latex synthesisconsisted of charging a reaction kettle with 493 g. of distilled water,54.4 g. of a 10% aqueous solution of the copolymer above prepared andheating to 89° C. under nitrogen. 164 g. of a 10% aqueous solution ofthe copolymer above prepared, styrene (218 g.) and ammonium persulfate(6 g. in 24.2 g. of distilled water) were added simultaneously over aperiod of two hours. The temperature was controlled at between 89°-96°C. After stirring for fifteen minutes the latex was cooled to roomtemperature and filtered through a 100-mesh screen. The filtered latexhad a solids content of 26%.

EXAMPLE 23

A reaction vessel was charged with 200 g. of distilled water, 0.24 g.acetic acid, 3.64 g. sodium acetate and 1.5 g. isopropanol. This washeated to 60°-62° C. under nitrogen and held for 15 minutes.Methylolacrylamide (40 g. in 160 g. distilled water),dimethyldiallylammonium chloride (13.3 g. in 53.1 g. distilled water)and ammonium persulfate (0.8 g. in 20 g. distilled water) were addedsimultaneously, dropwise, over a period of two hours followed bystirring for one hour. The copolymer solution, which had a solidscontent of 12.3%, was cooled to room temperature and the pH adjusted to7.3 with 0.5 cc. 5 M NaOH. A reaction kettle was charged with 439 g. ofdistilled water, 54.4 g. of a 10% aqueous solution of the abovecopolymer. The contents of the reaction kettle were heated to 88°-90° C.under nitrogen. 164 g. of a 10% aqueous solution of the above copolymer,218 g. styrene and 6 g. of ammonium persulfate in 24.2 cc. of distilledwater were added simultaneously, dropwise, over a period of about twohours to the reaction kettle. After addition was complete the contentsof the kettle were stirred for 15 minutes and cooled to roomtemperature. The resulting latex had a solids content of 25.4%.

EXAMPLE 24

A reaction vessel was charged with 170 cc. of distilled water and heatedto 85° C. under nitrogen sparge. After a 15 minute sparge, acrylamide(110.3 g. in 257.3 cc. distilled water), methyldiallylammonium acetate(133.2 g. of a 29.8% aqueous solution) and ammonium persulfate (7.5 g.in 71.3 cc. distilled water) were added simultaneously, dropwise, over aperiod of 1.75 hours followed by stirring 15 minutes and cooling. TotalSolids=20.4%, RSV=0.35 (1 M NaCl, 1%, 25° C.).

The latex synthesis consisted of charging 798 cc. of distilled water and1308 g. of a 10% aqueous solution of the copolymer prepared as above tothe reaction vessel. This was heated to 93° C. under nitrogen. Styrene(1308 g.), t-butylhydroperoxide (14.6 g. in 127.6 g. of distilled water)and sodium formaldehyde sulfoxylate (14.4 g. in 127.8 cc. distilledwater) were added simultaneously, dropwise, over a period of three hoursfollowed by stirring for 15 minutes and cooling to room temperature. Thelatex was filtered through a 100-mesh screen. Total Solids=39.7%.Particle size=0.65 micron--measured by the Loebel Method--see Table 5.

EXAMPLE 25

Glyoxal modification of the latex of Example 24 was carried out asfollows: 214 g. of the above latex was placed into a reaction vessel.The pH was adjusted from 4.9 to 8.5 with 1.4 cc. of 5 M NaOH. Glyoxal(9.3 g. in 13.9 g. distilled water) was added giving a pH of 6. This wasreadjusted to 8.5 with 1.3 cc. of 5 M NaOH. The latex-glyoxal mixturewas allowed to stir while maintaining the pH at 8.5 with periodicaddition of a total of 0.2 cc. 5 M NaOH. After about 30 minutes theviscosity increased from 31 to 60 cps. The reaction was terminated byadding 0.4 cc. of concentrated H₂ SO₄. Total solids=39.2%.

EXAMPLE 26

Latexes of Examples 24 and 25 were evaluated as fillers for paper by themethod described in Example 6. Results are set forth in Table 8 below.

                  TABLE 8                                                         ______________________________________                                                    Basis                                                                         Weight                                                                        (lb./   Tensile   Mullen                                                      3000    (lbs./    Burst Opacity.sup.(1)                           Filler (%)  sq. ft.)                                                                              in.)      (psi) %                                         ______________________________________                                        None        40.4    17.7      30.9  79.4                                      Example 24 (4)                                                                            41.2    17.4      32.5  86.2                                      Example 24 (8)                                                                            42.3    15.0      27.4  89.2                                      Example 25 (4)                                                                            41.5    19.5      35.9  86.3                                      Example 25 (8)                                                                            42.3    17.6      30.9  89.3                                      Kaolin Clay* (10)                                                                         44.2    15.2      22.0  86.2                                      Kaolin Clay* (20)                                                                         47.6    12.6      17.9  89.4                                      ______________________________________                                         *0.05% of a cationic polyacrylamide, based on the weight of the paper, wa     empolyed as a retention aid for the kaolin clay.                              .sup.(1) Opacity measured in accordance with Tappi Standard T425 (Diano       Opacimeter)                                                              

EXAMPLE 27

A water-jacketed resin kettle equipped with a thermometer, a stirrer, acondenser and four addition funnels was charged with 30.0 g. ofdistilled water, 0.6 g. acetic acid, and 0.85 g. sodium acetate. Thefunnels were charged with: (1) 60.0 g. styrene, (2) 6.0 g. chitosan, 6.0g. acetic acid, and 114.0 g. distilled water, (3) 0.65 g. of a 20%aqueous solution of t-butylhydroperoxide, and 25.0 g. distilled water,and (4) 0.65 g. sodium formaldehyde sulfoxylate and 25.0 g. distilledwater. The kettle contents were stirred and heated to 88° C. Thecontents of the four funnels were added, dropwise, over a period of fourhours as the kettle temperature was maintained at 60° C. After heatingfor an additional thirty minutes, the product was cooled to roomtemperature, not all styrene reacted and the unreacted styrene wasremoved with a rotary evaporator. The product was a latex having asolids content of 28.8%. The particles of this latex were evaluated aspaper fillers by the method of Example 6. Results are set forth in Table9 below.

                  TABLE 9                                                         ______________________________________                                                    Basis                                                                         Weight                                                                        (lb./              Tensile                                                                             Mullen                                               3000    Opacity.sup.(1)                                                                          (lbs./                                                                              Burst                                    Filler (%)  sq. ft.)                                                                              (%)        in.)  (psi)                                    ______________________________________                                        None        40.6    80.0       18.8  31.9                                     Example 27 (4)                                                                            40.8    84.1       18.5  28.8                                     Example 27 (8)                                                                            41.9    86.6       17.7  28.5                                     Kaolin Clay* (10)                                                                         44.6    85.7       15.2  23.0                                     Kaolin Clay* (20)                                                                         46.3    87.5       13.3  18.6                                     Commercial  41.0    83.5       17.7  28.3                                     Polystyrene* (4)                                                              Commercial  41.2    86.1       16.3  26.3                                     Polystyrene* (8)                                                              ______________________________________                                         *0.05% of cationic polyacrylamide, based on the weight of the paper, was      employed as a retention aid for the filler.                                   .sup.(1) Opacity measured in accordance with Tappi Standard T425 (Hunter      Opacity Meter).                                                          

The unique advantages of the organic pigments of this invention can bestbe illustrated by considering the data in Tables 1 and 2. The organicpigments were added in amounts of 4% and 8% and were compared to kaolinclay added in amounts of 10% and 20% (equivalent in volume to 4% and 8%of the organic pigments of this invention). Alum and a high molecularweight cationic polyacrylamide were used as retention aids for thekaolin clay. No retention aid was used with the organic pigments of thisinvention. The opacity of filled paper is a measure of the retention ofthe filler in the paper.

The dry tensile and Mullen Burst data in Table 2 illustrate the strengthadvantages provided by the organic pigments of the present invention. Itcan be seen that kaolin clay decreases the strength properties relativeto unfilled paper by about 20-30%. In contrast, the organic pigments ofthis invention that give the highest opacity (compositions of Examples 3and 4) also give strength improvements of about 5-15% relative tounfilled paper. Comparing these organic pigments to clay, the formergive opacity equivalent to the latter and in addition, have strengthproperties 20-50% higher than the latter.

One further advantage of the fillers (organic pigments) of thisinvention is evident in Table 2. The clay-filled paper is considerablyheavier than the control, while the paper containing the filler of thisinvention is only slightly heavier than the control.

The data in Tables 3 and 4 summarize the evaluation of a similar seriesof organic pigments stabilized using acrylamidedimethyldiallylammoniumchloride copolymers as the water-soluble cationic prepolymer but notreacted with glyoxal. Because there is no reactive functionality on theparticles, the strength properties were poorer in this experiment thanin the previous one.

The data in Tables 5 and 6 summarize a similar experiment in which theorganic pigments were prepared using various copolymers of acrylamideand methacryloyloxyethyltrimethylammonium methyl sulfate as thewater-soluble cationic prepolymer. Since there was no reactivefunctionality on the particles, strength values were slightly poorerthan the control in some cases but always significantly better than forthe clay-filled paper. For further comparison, a commercially availablepolystyrene latex was evaluated in this experiment. The particles inthis latex have anionic charges, so alum and a polymeric retention aidwere used. The data show that the polystyrene particles gave paperhaving slightly higher opacity than the organic pigments of thisinvention (but also higher basis weight). The polystyrene particlesdecreased paper strength, although not quite as much as did the clay.

The data in Table 7 show that conventional fillers like clay andpolystyrene require retention aids for optimum performance. Withoutretention aids opacity is very low in both cases. As shown in Tables 2,4 and 6, the organic pigments of the present invention provide goodopacity without the use of any retention aid.

EXAMPLE 26

A water-jacketed reaction vessel fitted with a thermommometer, astirrer, a condenser, and an addition funnel was charged with 89 gramsdistilled water and 436 grams of a 10% aqueous solution ofpoly(methyldiallylammonium chloride). The resulting solution was heatedto 87°-88° C. by circulating hot water through the jacket of thereaction vessel. Styrene (425.2 grams) and divinylbenzene (10.9 grams)were mixed and placed in the addition funnel. 13.3 Grams of a 90%aqueous solution of t-butylhydroperoxide and 108 grams of distilledwater were placed in a burette; and 13.6 grams of sodium bisulfitedissolved in 124.5 grams distilled water were placed in another burette.The mixture of styrene and divinylbenzene; the t-butylhydroperoxidesolution; and the sodium bisulfite solution were added dropwise,simultaneously, over a period of 2 hours to the contents of the reactionvessel. After stirring for 20 minutes, a slight odor of styrene wasevident. Additional t-butylhydroperoxide solution (3.4 grams oft-butylhydroperoxide dissolved in 27 grams distilled water) andadditional sodium bisulfite solution (3.4 grams sodium bisulfitedissolved in 31 grams of distilled water) were added to the reactionmass and the reaction mass was stirred for an additional 20 minutes. Theresulting latex was cooled to room temperature and filtered through a100 mesh screen. Total solids=27.7%. Particle size=0.8 micron--measuredby Coulter Counter.

As previously set forth, polyethylenically unsaturated monomers, such asdivinylbenzene, can be used in admixture with monoethylenicallyunsaturated monomers to provide crosslinked graft copolymer particles.Examples of other suitable polyethylenically unsaturated monomers thatcan be used for this purpose are diallyl phthalate, ethylene glycoldimethacrylate, 1,3-hexanediol dimethacrylate, polyethylene glycoldimethacrylate, polypropylene glycol dimethacrylate, trivinylbenzene,divinylnaphthalene, diallyl maleate, diallyl fumarate, trimethylolpropane trimethacrylate, and pentaerythritol tetraacrylate. Thepreferred polyethylenically unsaturated monomers, also referred to ascrosslinking monomers, are divinylbenzene, diallyl phthalate, ethyleneglycol dimethacrylate, and 1,3-butylene glycol dimethacrylate.

While the organic pigments of this invention have particular utility aspaper fillers, they can also be used in paper coatings together with asuitable binder therefor. Furthermore, they can be used in paints, inks,and the like. They can also be applied as coatings, together with asuitable binder, to glass surfaces, metal surfaces, wood surfaces,plaster surfaces and the like.

EXAMPLE 29

A water-jacketed resin kettle equipped with a thermometer, a stirrer, acondenser and three addition funnels was charged with 75.0 g. ofdistilled water. The funnels were charged as follows: funnel (1) with35.0 g. acrylamide (0.49 mole) in 70.0 g. distilled water, funnel (2)with 15.0 g. vinylbenzyltrimethylammonium chloride (0.07 mole) in 60.0g. distilled water, and funnel (3) with 1.25 g. ammonium persulfate in50.0 g. distilled water. The kettle contents were heated to 80° C., andthe contents of the funnels were added, dropwise, over a period of 21/2hours as the temperature was maintained at 80°-85° C. After heating foran additional 30 minutes, the solution was cooled to room temperature(about 23° C.). The product solution contained 22.0% solids and had anRSV, reduced specific viscosity, of 0.27 (1% solution in 1 M NaCl, 25°C.).

A water-jacketed resin kettle fitted with a thermometer, a stirrer, acondenser and three addition funnels was charged with 503.8 g. ofdistilled water and 26.2 g. of the above copolymer solution (5.8 g. drycopolymer). The funnels were charged as follows: funnel (1) with 78.6 g.of the above copolymer solution (17.3 g. dry copolymer) plus 120.0 g.distilled water, funnel (2) with 230.0 g. styrene, and funnel (3) with5.1 g. ammonium persulfate in 120.0 g. distilled water. The kettlecontents were stirred and heated to 79° C. The contents of the threefunnels were added, dropwise, over a period of four hours as the kettletemperature was maintained at 79°-88° C. After heating for an additional15 minutes, the product was cooled to room temperature, and the pH wasadjusted from 1.9 to 7.5 with 25% sodium hydroxide solution. The productwas filtered through a 100 mesh sieve. The product was a white latexcontaining 25.1% total solids and having an average particle size of0.62 micron (method of A. B. Loebel, Official Digest, 200, February,1959).

EXAMPLE 30

A water-jacketed resin kettle equipped with a thermometer, a stirrer, acondenser and two addition funnels was charged with 200 g. of distilledwater. The funnels were charged as follows: funnel (1) with 77.0 g.acrylamide (1.08 mole), 17.1 g. 4-vinylpyridine (0.16 mole), and 16.0 g.concentrated hydrochloric acid solution (0.19 mole) in 200 g. distilledwater, and funnel (2) with 2.5 g. ammonium persulfate in 100 g.distilled water. The kettle contents were heated to 80° C., and thecontents of the funnels were added, dropwise, over a period of 2 hours,25 minutes as the temperature was maintained at 80°-85° C. After heatingfor an additional 30 minutes, the solution was cooled to roomtemperature (about 23° C.). The product solution contained 21.6% solidsand had an RSV, reduced specific viscosity, of 0.34 (1% solution in 1 MNaCl, 25° C.).

A water-jacketed resin kettle fitted with a thermometer, a stirrer, acondenser and three addition funnels was charged with 503.4 g. ofdistilled water and 26.6 g. of the above copolymer solution (5.7 g. drycopolymer). The funnels were charged as follows: funnel (1) with 79.8 g.of the above copolymer solution (17.2 g. dry copolymer) plus 120 g.distilled water, funnel (2) with 230 g. styrene, and funnel (3) with 5.1g. ammonium persulfate in 120.0 g. distilled water. The kettle contentswere stirred and heated to 78° C. The contents of the funnels wereadded, dropwise, at the same time. The contents of funnels (1) and (2)were added over a period of 4 hours. The contents of funnel (3) wereadded over a period of 4 hours, 15 minutes. The kettle temperature wasmaintained at 78°-84° C. throughout the additions. The product wascooled to room temperature, and the pH was adjusted from 2.0 to 4.6 with10% sodium hydroxide solution. The product was filtered through a 100mesh sieve. The product was a white latex containing 25.8% total solidsand having an average particle size of 0.45 micron (method of Loebel,Official Digest, 200, February, 1959).

EXAMPLE 31

A water-jacketed resin kettle equipped with a thermometer, a stirrer, acondenser and two addition funnels was charged with 200 g. of distilledwater. The funnels were charged as follows: funnel (1) with 69.0 g.acrylamide (0.97 mole) and 31.0 g. methacrylamidopropyltrimethylammoniumchloride (0.14 mole) in 200 g. distilled water, and funnel (2) with 2.5g. ammonium persulfate in 100 g. distilled water. The kettle contentswere heated to 77° C., and the contents of the funnels were added,dropwise, over a period of 21/2 hours as the temperature was maintainedat 77°-85° C. After heating for an additional 15 minutes, the solutionwas cooled to room temperature (about 23° C.). The product solutioncontained 22.7% solids and had an RSV, reduced specific viscosity, of0.52 (1% solution in 1 M NaCl, 25° C.).

A water-jacketed resin kettle fitted with a thermometer, a stirrer, acondenser and three addition funnels was charged with 504.7 g. ofdistilled water and 25.3 g. of the above copolymer solution (5.7 g. drycopolymer). The funnels were charged as follows: funnel (1) with 76.1 g.of the above copolymer solution (17.3 g. dry copolymer) and 120.0 g.distilled water, funnel (2) with 230.0 g. styrene, and funnel (3) with5.1 g. ammonium persulfate in 120 g. distilled water. The kettlecontents were stirred and heated to 79° C. The contents of the funnelswere added, dropwise, at the same time. The contents of funnels (1) and(2) were added over a period of 4 hours. The contents of funnel (3) wereadded over a period of 4 hours, 15 minutes. The kettle temperature wasmaintained at 79°-87° C. throughout the additions. The product wascooled to room temperature, and the pH was adjusted from 2.1 to 8.0 with25% sodium hydroxide solution. The product was filtered through a 100mesh sieve. The product was a white latex containing 25.5% total solidsand having an average particle size of 0.47 micron (method of Loebel,Official Digest, 200, February, 1959).

EXAMPLE 32

A water-jacketed resin kettle equipped with a thermometer, a stirrer, acondenser and two addition funnels was charged with 200 g. of distilledwater. The funnels were charged as follows: funnel (1) with 67 g.acrylamide (0.94 mole) and 33 g.3-methacryloyloxy-2-hydroxypropyltrimethylammonium chloride (0.14 mole)in 200 g. distilled water, and funnel (2) with 2.5 g. ammoniumpersulfate in 100 g. distilled water. The kettle contents were heated to80° C., and the contents of the funnels were added, dropwise, over aperiod of 2 hours, 25 minutes as the temperature was maintained at80°-84° C. After heating for an additional 15 minutes, the solution wascooled to room temperature (about 23° C.). The product solutioncontained 21.3% solids and had an RSV, reduced specific viscosity, of0.46 (1% solution in 1 M NaCl, 25° C.).

A water-jacketed resin kettle fitted with a thermometer, a stirrer, acondenser and three addition funnels was charged with 503 g. ofdistilled water and 27 g. of the above copolymer solution (5.8 g. drycopolymer). The funnels were charged as follows: funnel (1) with 81 g.of the above copolymer solution (17.3 g. dry copolymer) and 120 g.distilled water, funnel (2) with 230 g. styrene, and funnel (3) with 5.1g. ammonium persulfate in 120 g. distilled water. The kettle contentswere stirred and heated to 77° C. The contents of the funnels wereadded, dropwise, at the same time. The contents of funnels (1) and (2)were added over a period of 4 hours. The contents of funnel (3) wereadded over a period of 4 hours, 15 minutes. The kettle temperature wasmaintained at 77°-88° C. throughout the additions. The product wascooled to room temperature, and the pH was adjusted from 1.9 to 6.5 with25% sodium hydroxide solution. The product was filtered through a 100mesh sieve. The product was a white latex containing 25.5% total solidsand having an average particle size of 0.8 micron (method of Loebel,Official Digest, 200, February, 1959).

EXAMPLE 33

The compositions of Examples 29-32 were evaluated as fillers for paper.Handsheets were prepared on a Noble & Wood handsheet apparatus. The pulpconsisted of a 50:50 blend of bleached hardwood:bleached softwood pulpsbeaten to a Canadian Standard Freeness of 500. The paper was made at apH of 4.5 (sulfuric acid, no alum). The latexes were evaluated ataddition levels of 4% and 8% (dry basis). The control was unfilledpaper. The results of testing of the paper are sumarized in Table 10below.

                  TABLE 10                                                        ______________________________________                                                  Basic                  Dry                                                    Weight    Opa-   Bright-                                                                             Tensile.sup.3                                                                        Mullen.sup.3                                    (lb./3000 city.sup.1                                                                           ness.sup.2                                                                          Strength                                                                             Burst                                 Filler (%)                                                                              sq. ft.)  (%)    (%)   (lb./in.)                                                                            (psi)                                 ______________________________________                                        None          39.6      73.4 80.2  19.2   31.0                                Example 29                                                                            (4)   40.4      78.4 81.6  19.4   32.5                                        (8)   41.0      83.0 82.6  18.1   30.6                                Example 30                                                                            (4)   42.1      79.2 83.6  21.9   33.5                                        (8)   40.9      83.0 85.5  21.5   32.9                                Example 31                                                                            (4)   41.6      78.3 82.8  19.6   30.7                                        (8)   41.5      81.4 83.1  21.0   33.3                                Example 32                                                                            (4)   39.3      75.3 79.8  20.6   31.0                                        (8)   41.6      80.8 83.6  21.5   31.4                                ______________________________________                                         .sup.1 Opacity measured in accordance with Tappi Standard T425 (Diano         Opacity Meter) average of 4 tests                                             .sup.2 Brightness measured in accordance with Tappi Standard T452 (Diano      Brightness Meter) average of 4 tests                                          .sup.3 Average of 8 tests                                                

The novel organic pigments of this invention can be used alone or incombination with other organic pigments, or inorganic pigments or bothas fillers and coatings for paper.

The above description and examples are illustrative of this inventionand not in limitation thereof.

What we claim and desire to protect by Letters Patent is: 1.Water-insoluble graft copolymer particles consisting essentially of thefree radical catalyzed graft copolymerization product of (1) at leastone ethylenically unsaturated monomer (a) and at least onepolyethylenically unsaturated monomer (b) in an amount at leastsufficient to provide cross linked graft copolymer particles, and (2) awater-soluble cationic prepolymer having an RSV of about 0.1 to about1.0 (1 M NaCl, 1%, 25° C.), the prepolymer moiety of the graft copolymerparticles being present on the surface of the particles,said monomer (a)being a monomer having the formula ##STR20## wherein R is hydrogen ormethyl, Y is methyl or chlorine, and n is 0, 1, 2, or 3, said monomer(b) being selected from the group consisting of divinylbenzene; diallylphthalate; ethylene glycol dimethacrylate; 1,3-butylene glycoldimethacrylate; 1,6-hexane diol dimethacrylate; polyethylene glycoldimethacrylate; polypropylene glycol dimethacrylate; trivinylbenzene;divinylnaphthalene; diallyl maleate; diallyl fumarate; trimethylolpropane trimethacrylate; and pentaerythritol tetraacrylate, and saidprepolymer (2) being the addition polymerization product of(i) about 5mole percent to 100 mole percent of a cationic monomer having theformula ##STR21## wherein R₁ is hydrogen or methyl, R₃ is hydrogen, a C₁-C₄ alkyl, ##STR22## where Y is hydroxyl or halogen, ##STR23## and --CH₂CH₂ O)_(n) H where n is an integer 1 or more and X⁻ is an anion, and(ii) from about 95 mole percent to 0 mole percent of at least onemonoethylenically unsaturated amide monomer,the amount of prepolymer (2)employed in preparing the graft copolymer particles being from about 2parts to about 10 parts by weight for each 100 parts by weight ofmonomer (1) employed.
 2. The water-insoluble graft copolymer particlesof claim 1 wherein monomer (a) is styrene and the monoethylenicallyunsaturated amide monomer is acrylamide.
 3. The water-insoluble graftcopolymer particles of claim 1 wherein monomer (a) is styrene, themonoethylenically unsaturated amide monomer is acrylamide, and cationicmonomer (i) is selected from the group consisting of 2-vinylpyridiniumchloride and 2-vinylpyridinium bromide.
 4. A process for preparing alatex of graft copolymer particles which comprises graft copolymerizingin aqueous media and in the presence of a free-radical initiator (1) atleast one ethylenically unsaturated monomer (a) and at least onepolyethylenically unsaturated monomer (b) in an amount at leastsufficient to provide cross linked graft copolymer particles, and (2) awater-soluble cationic prepolymer having an RSV of about 0.1 to about1.0 (1 M NaCl, 1%, 25° C.),said monomer (a) being a monomer having theformula ##STR24## wherein R is hydrogen or methyl, Y is methyl orchlorine, and n is 0, 1, 2, or 3, said monomer (b) being selected fromthe group consisting of divinylbenzene; diallyl phthalate; ethyleneglycol dimethacrylate; 1,3-butylene glycol dimethacrylate;1,6-hexanediol dimethacrylate; polyethylene glycol dimethacrylate;polypropylene glycol dimethacrylate; trivinylbenzene;divinylnaphthalene; diallyl maleate; diallyl fumarate; trimethylolpropane trimethacrylate; and pentaerythritol tetraacrylate, and saidprepolymer (2) being the addition polymerization product of(i) about 5mole percent to 100 mole percent of a cationic monomer having theformula ##STR25## wherein R₁ is hydrogen or methyl, R₃ is hydrogen, a C₁-C₄ alkyl, ##STR26## where Y is hydroxyl or halogen, ##STR27## and --CH₂CH₂ O)_(n) H where n is an integer 1 or more and X⁻ is an anion, and(ii) from about 95 mole percent to 0 mole percent of at least onemonoethylenically unsaturated amide monomer,and the amount of prepolymer(2) employed in preparing the graft copolymer particles being from about2 parts to about 10 parts by weight for each 100 parts by weight ofmonomers (1) employed.
 5. The process of claim 4 wherein monomer (a) isstyrene and the monoethylenically unsaturated amide monomer isacrylamide.
 6. The process of claim 4 wherein monomer (a) is styrene,the monoethylenically unsaturated amide monomer is acrylamide andcationic monomer (i) is selected from the group consisting of2-vinylpyridinium chloride and 2-vinyl pyridinium bromide.